Mineralogical study of archaeological copper slags found in the area of the Boyadzhik village, Yambol region, Southeast Bulgaria

Tzankova, N., D. Stavrakeva. 2020. Mineralogical study of archaeological copper slags found in the area of the Boyadzhik village, Yambol region, Southeast Bulgaria. -Journal of Mining and Geological Sciences, Volume 63, 2020, 267-271.

ABSTRACT. In this paper, we present the results from a phase-chemical and structural study of metallurgical slags, found in an archaeological site near the village of Boyadzhik, Yambol region. The studied samples are mainly composed of SiO2 (37.22 – 37.45 %), Fe2O3 (36.26 – 36.71 %), CaO (11.11 – 11.66 %) and Al2O3 (6.03 – 6.15 %). The dominant phase is fayalite, followed by magnetite and maghemite, augite, and augite-type pyroxene closest to esseneite. These minerals were observed microscopically in transmitted and reflected light and were established by XRD study and SEM CDD-EDS microanalyses. The copper in the studied slags goes up to 2.46 % indicating low process efficiency of copper extraction from the raw material. The copper was presented by metallic droplets as well as copper-oxide and copper-iron-oxide phases. No relics of sulfide minerals and sulfur-containing phases were found in the analyzed samples. The mineral composition of the studied samples and their structural and phase peculiarities allow us to define these materials as by-products (slags) from copper-containing oxidic ore smelting.

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